State of the Planet

News from the Columbia Climate School

Closing Out Climate Week: Why 2 Degrees is Too High for the Cryosphere

The melting Greenland ice sheet. Photo: UN Photo

What’s the big deal about half a degree? According to people who study the cryosphere—i.e., all the frozen water on Earth, such as glaciers and continental ice sheets—it’s the only thing standing between us and devastating global climate impacts. 

“1.5 degrees Celsius versus current policies [of 2 degrees Celsius] makes all the difference in the world,” according to Robert DeConto, an Intergovernmental Panel on Climate Change (IPCC) author. If we allow the increase in global average temperatures to reach 2 degrees Celsius above pre-industrial levels, the two massive polar ice sheets—Greenland and Antarctica—could rapidly lose ice and raise global sea levels up to 15 meters, DeConto said.

DeConto was speaking at a landmark science-policy event, The Road to COP 28: Melting Ice, Rising Seas, and Why 2 Degrees Celsius is Too High, as part of this year’s Climate Week NYC 2023. The event, organized by the Ambition on Melting Ice (AMI) and the International Cryosphere Climate Initiative (ICCI), and hosted by New York’s Explorers Club, underscored the critical role of snow and ice science in global decision making. Co-chaired by Chile and Iceland, AMI represents not only polar and mountain nations, but also low-lying and downstream countries that endure the devastating impacts of cryosphere loss. 

A presentation on Antarctica by IPCC author Robert DeConto. Photo: Amy Imdieke
A presentation on Antarctica by IPCC author Robert DeConto. Photo: Amy Imdieke

With only 10 weeks remaining before COP 28, AMI nations convened top scientists at this event to amplify the latest cryosphere findings in the formal negotiations. Ministers, ambassadors and scientists all highlighted efforts to define 1.5 degrees, rather than 2 degrees, as the necessary upper-temperature limit to stave off the worst impacts of climate change. Their message: Taking 2 degrees off the table requires urgent, decisive and collaborative action between governments at COP 28 in Dubai this December.

Scientists Warn About the Global Impacts of Snow and Ice Loss

The Norwegian Minister of Climate and the Environment Espen Barth-Eide opened the event. “People need to care about the Arctic because what happens in the Arctic does not stay in the Arctic,” Barth-Eide said. “It’s a symbol of something serious going on in the planet that we share.”

Espen Barth-Eide, Minister of Climate and Environment, Norway. Photo: Amy Imdieke
Espen Barth-Eide, minister of climate and environment, Norway. Photo: Amy Imdieke

Speakers from ministers to IPCC authors provided a strong call to action in response to the realities of melting ice and sea level rise. “Advancing mitigation and ambition is the most effective way to conserve and preserve our cryosphere,” said Julio Cordano, director of environment, climate change and oceans for the Chilean Ministry of Foreign Affairs. “If we knew in 2015 what we know today about the global cryosphere, 2 degrees Celsius would have been off the table as a viable temperature goal of the Paris Agreement,” said Pam Pearson, director of the AMI Secretariat and ICCI.

Another theme of the event: Where ice sheets bring devastating sea level rise, retreating mountain glaciers and shrinking snowpack pose a grave threat to water security. 

Mira Khadka, a Ph.D. student from Nepal studying at Carnegie Mellon, explained how exceeding 1.5 degrees Celsius will lead to centuries of impacts on global water resources. “At 2 degrees, nearly all tropical glaciers and most of the mid-latitude glaciers will disappear. In the Hindu Kush Himalaya, almost 50% of all glacier ice that we have today will be lost,” said Khadka. “There are millions of people living in the mountains and billions of people living downstream who rely on these freshwater resources for drinking, hydropower, agriculture and so much more.”

“I have personally experienced the impacts of climate change from flooding to avalanches, and also this feeling of helplessness when our voices are ignored,” said Khadka. “The mountain communities back home in High Mountain Asia are already struggling with poverty and geopolitical issues; climate change is making that worse.”

According to the soon-to-be-published State of the Cryosphere 2023 report—last year’s report can be downloaded here—the impacts of warming on mountain communities are unfolding around the world. Between 2022 and 2023, the Swiss Alps lost 10% of their glacier ice. In the Southern Hemisphere, Argentina and Chile experienced record high temperatures this past winter, which will cause unprecedented water shortages. Norway already experienced hydropower shortages last year due to low snowpack.

Pearson summarized the long-tailed legacy of polar ocean acidification, warming and freshening. She made clear the importance of urgent emissions reductions to ensure that oceans remain a livable environment for polar species. “It’s important to think about how unprecedented CO2 levels are today. At 424ppm, 2023 will be remembered as the year that CO2 levels reached 50% above pre-industrial levels,” she said.

Urgent Action to Uphold 1.5 Degrees 

IPCC author Christina Schaedel from the Woodwell Climate Research Center described the vulnerability of permafrost (permanently frozen ground containing a mixture of ice, rocks, soil and organic matter). Rising temperatures thaw the ground and release stored carbon as CO2 and methane, creating a “vicious cycle” that amplifies warming. Even with 1.5 degrees, frozen permafrost stores would release 150-200 gigatons of CO2 by the end of the century, equivalent to the cumulative emissions from some national emitters today. These permafrost emissions could more than double if global temperatures remain on their current trajectory, Schaedel said. 

Twila Moon, deputy lead scientist at the National Snow and Ice Data Center (NSIDC), explained how warming of 1.5-1.7 degrees serves as a threshold for polar sea ice. “Since 1979, we have seen a 13% decrease in Arctic sea ice extent every decade,” said Moon. “The past 17 years have been the lowest 17 years of Arctic sea ice extent. We know this represents a direct relationship between how many tons of CO2 are in the atmosphere and the area of sea ice lost.”

Twila Moon, NSIDC, at the event. Photo: Amy Imdieke
Twila Moon, NSIDC. Photo: Amy Imdieke

Moon also discussed how ice loss is happening faster than expected. At only 1.7 degrees, we will experience the full loss of summer sea ice in the Arctic, without any remaining multi-year sea ice to support local habitats or protect coastal communities from erosion, storms and waves. Antarctic sea ice, which is now setting records of minimum area, plays a role in stabilizing the Antarctic ice sheet. Loss of this protective layer of floating ice will only increase the continent’s ice vulnerability to future warming.

Speaking after the science presentations, Ashok Adicéam, head of global affairs for the 2025 UN Ocean Conference, announced that France will join AMI at its November 8-10 One Planet Polar Summit in Paris. Other nations are expected to officially join AMI at COP 28.

“Climate change presents one of the biggest threats to humanity in recorded history, and is by far the most dire and pressing problem facing the world today,” said Page Fortna, Harold Brown professor of U.S. Foreign and Security Policy at Columbia University, who was not personally involved in the event. “The economic costs, as well as the threats to national and human security, are already being felt in the U.S. and around the globe; they will only get worse if we do not act quickly and aggressively to transition away from fossil fuels.”

A recording of the event can be viewed here

Banner featuring a collage of extreme heat images.

Recent record-breaking heat waves have affected communities across the world. The Extreme Heat Workshop will bring together researchers and practitioners to advance the state of knowledge, identify community needs, and develop a framework for evaluating risks with a focus on climate justice. Register by June 15

Notify of

Inline Feedbacks
View all comments